1. Field of the Invention
The present invention relates to a display device element substrate and a method of manufacturing the same and, more particularly, a display device element substrate having various elements employed in an EL display device, a liquid crystal display device, or the like and a method of manufacturing the same.
2. Description of the Related Art
In recent years, the range of use of the display device such as the liquid crystal display device, the organic EL (Electroluminescence) display device, or the like is expanding rapidly to the information equipment, and so forth. In these display devices, the element substrate having various dot matrix elements corresponding to the simple matrix system or the active matrix system is employed. As the dot matrix element, the stripe-like transparent electrode is employed in the simple matrix system whereas the active element such as the TFT (Thin Film Transistor) element, the MIM (Metal Insulator Metal) element, or the like is employed in the active matrix system.
For the purpose of weight reduction, breakage prevention, et al., instead of the glass substrate, the plastic film may be employed as the base substrate of such element substrate. Since the plastic film has a small rigidity and a low heat deformation temperature, the thermal deformation such as bowing, expansion and contraction, or the like is ready to occur during the manufacturing process including the annealing.
For this reason, in the manufacturing method of forming directly the dot matrix elements, the color filter layers, etc. on the plastic film, conditions of the manufacturing steps including the annealing, etc. are restricted and also high-accuracy alignment becomes difficult. As a result, in some cases, the element substrate with desired characteristics cannot be manufactured.
In order to avoid such problem, there is the method of manufacturing the display device element substrate by forming the dot matrix elements, the color filter layers, etc. on the heat-resistant rigid glass substrate without any limitation of the manufacturing conditions in high-accuracy alignment to get the transfer layer, and then transferring/forming this transfer layer on the plastic film (for example, Patent Literature 1 (Patent Application Publication (KOKAI) 2003-131199)).
Meanwhile, in the organic EL element employed in the organic EL display device, the spot-like or circle-like nonemissive display defect called the dark spot is liable to occur because separation between the electrodes and the organic EL layer makes progress due to penetration of a water vapor, or the like.
In the above organic EL display device employing the plastic film as the substrate, measures are required to prevent the penetration of not only the water vapor entered from the outside air but also a moisture content contained in the plastic film itself into the organic EL element. Also, in the liquid crystal display device employing the plastic film as the substrate, there is a danger that the display characteristics are deteriorated similarly because the moisture content or the gas penetrates into the liquid crystal layer.
As the measure, it may be considered that a silicon nitride layer is formed on the whole surface of the plastic film on the element forming surface side as the barrier layer. However, a film thickness of the silicon nitride layer must be set relatively thick to secure the sufficient barrier property and the thick silicon nitride layer becomes colored. As a result, such a problem lies that the display characteristics of the display device are deteriorated.
In the above Patent Literature 1, no regard is paid to the problem that the display characteristics of the display device are deteriorated due to the penetration of the water vapor.